In recent years, flat panel display devices that use flat panel display elements such as liquid crystal panels and plasma display panels are increasingly used as display elements for image display devices such as television receivers instead of conventional cathode-ray tube displays, allowing image display devices to be made thinner. Liquid crystal panels used in liquid crystal display devices do not emit light on their own, and therefore, it is necessary to provide a separate backlight device as an illumination device. In such backlight devices, generally, light source is housed in a chassis that functions as a case, and a circuit substrate on which a plurality of electronic components for supplying power to the light source, performing drive control on the light sources, and the like are attached to the outer side of the chassis.
Patent Document 1 discloses a backlight device including such a circuit substrate. A circuit substrate is attached to the backlight device so as to have the surface thereof opposite to where the electronic components are mounted face the chassis. The chassis additionally has attached thereto another member such as a substrate cover covering the mounting surface for the electronic components. In such a configuration, heat generated from the electronic components on the circuit substrate is transmitted towards the substrate cover facing the electronic components, and is dissipated from the other member to outside of the backlight device.